1. Field of Disclosure
The present disclosure relates generally to valves, and more particularly to globe valves that are used in HVAC systems.
2. Discussion of Related Art
In heating, ventilation, and air conditioning (HVAC) systems, globe valves are used for applications requiring throttling and shut off with an actuator that provides an operating force to aid in closing and opening of the valve as required. The force required to operate a typical valve depends on many factors, such as valve size, operating pressure, and sealing design, for example.
A typical globe valve includes a generally spherical body with two halves of the spherical body being separated by an internal baffle, which has an opening formed therein. The opening creates a valve seat in which a movable valve or plug is seated. An actuator, either manual or automatic, can be used to manipulate the movement of the plug to open and close the valve.
FIG. 1 illustrates an unbalanced globe valve 2 having a solid plug 4. Although presently available unbalanced globe valves may perform efficiently, such valves require large forces to operate, thereby demanding a stronger and more expensive actuator. With an unbalanced globe valve 2, the force needed to close-off the plug 4 is dependent primarily on the pressure exerted on the area of the plug. Due to these system operation pressures in the system, an actuator must provide a sufficient force to move the plug. Unbalanced globe valves having solid plugs are relatively simple in design, and are primarily used when smaller valve sizes are required.
FIG. 2 illustrates a balanced valve 6 having a plug 8, which has large cavities formed in the plug to enable fluid to flow through the plug. Balanced globe valves having plugs with large cavities or openings are more complex in design, and are primarily used when larger valves are required. Reference can be made to U.S. Pat. No. 7,017,608, which discloses a balanced globe valve design.